Electrical connectors provide signal connections between electronic devices using signal contacts. Often, the signal contacts are so closely spaced that undesirable interference, or “cross talk,” occurs between adjacent signal contacts. As used herein, the term “adjacent” refers to contacts (or rows or columns) that are next to one another. Cross talk occurs when one signal contact induces electrical interference in an adjacent signal contact due to intermingling electrical fields, thereby compromising signal integrity. With electronic device miniaturization and high speed, high signal integrity electronic communications becoming more prevalent, the reduction of cross talk becomes a significant factor in connector design.
One commonly used technique for reducing cross talk is to position separate electrical shields, in the form of metallic plates, for example, between adjacent signal contacts. Another commonly used technique to block cross talk between signal contacts is to place ground contacts amongst the signal contacts of a connector. The shields and ground contacts act to block cross talk between the signal contacts by blocking the intermingling of the contacts' electric fields. FIGS. 1A and 1B depict exemplary contact arrangements for electrical connectors that use shields to block cross talk.
FIG. 1A depicts an arrangement in which signal contacts S and ground contacts G are arranged such that differential signal pairs S+, S− are positioned along columns 101–106. As can be seen in FIG. 1A, the signal pairs are edge coupled (i.e., where the edge of one contact is adjacent to the edge of an adjacent contact). Shields 112 can be positioned between contact columns 101–106. A column 101–106 can include any combination of signal contacts S+, S− and ground contacts G. The ground contacts G serve to block cross talk between differential signal pairs in the same column. The shields 112 serve to block cross talk between differential signal pairs in adjacent columns.
FIG. 1B depicts an arrangement in which signal contacts S and ground contacts G are arranged such that differential signal pairs S+, S− are positioned along rows 111–116. As can be seen in FIG. 1B, the signal pairs are broadside-coupled (i.e., where the broad side of one contact is adjacent to the broad side of an adjacent contact). Shields 122 can be positioned between rows 111–116. A row 111–116 can include any combination of signal contacts S+, S− and ground contacts G. The ground contacts G serve to block cross talk between differential signal pairs in the same row. The shields 122 serve to block cross talk between differential signal pairs in adjacent rows.
Because of the demand for smaller, lower weight communications equipment, it is desirable that connectors be made smaller and lower in weight, while providing the same performance characteristics. Shields and ground contacts take up valuable space within the connector that could otherwise be used to provide additional signal contacts, and thus limit contact density (and, therefore, connector size). Additionally, manufacturing and inserting such shields and ground contacts substantially increase the overall costs associated with manufacturing such connectors. For example, in some applications, shields are known to make up 40% or more of the cost of the connector. Another known disadvantage of shields is that they lower impedance. Thus, to make the impedance high enough in a high contact density connector, the contacts would need to be so small that they would not be robust enough for many applications. Furthermore, ground contacts can take up a large percentage of the available contacts in a connector, thus causing an increase in size and weight of the connector for a given number of differential signal pairs.
Therefore, a need exists for a lightweight, high-speed electrical connector that reduces the occurrence of cross talk without the need for separate shields or ground contacts, and provides for a variety of other benefits not found in prior art connectors. More particularly, what is needed is an impedance-controlled insert molded leadframe assembly (IMLA) that maintains a distance between broadside coupled signal pairs such that cross-talk between signal pairs may be limited without the use of shields or ground contacts.